plotting.py 文件源码

def contract_positions(XY, edges, stepsize):
    """Perturb vertex positions by an L1-minimizing attractive force.

    This is used to slightly adjust vertex positions to provide a visual
    hint to their grouping.

    Args:
        XY: A [V, 2]-shaped numpy array of the current positions.
        edges: An [E, 2]-shaped numpy array of edges as (vertex,vertex) pairs.

    """
    E = edges.shape[0]
    V = E + 1
    assert edges.shape == (E, 2)
    assert XY.shape == (V, 2)
    old = XY
    new = old.copy()
    heads = edges[:, 0]
    tails = edges[:, 1]
    diff = old[heads] - old[tails]
    distances = (diff**2).sum(axis=1)**0.5
    spacing = distances.min()
    assert spacing > 0
    diff /= distances[:, np.newaxis]
    diff *= spacing
    new[tails] += stepsize * diff
    new[heads] -= stepsize * diff
    return new